GENERAL CHEMISTRY OF MILK 



MILK is composed of simple and complex substances which are 

 so balanced as to meet the requirements of young mammals. 

 The milk of different species of mammals varies greatly in com- 

 position, as shown in the following table (compiled from various 

 sources) : 



COMPOSITION OF THE MILK OF DIFFERENT MAMMALS 



There are distinct groups of compounds which are contained 

 in all milks, although in different proportion. These groups are: 



1. Fat. 



2. Proteins. 



3. Carbohydrate. 



4. Salts. 



5. Water. 



In addition, there are other substances present in small 

 amounts, namely: lecithin, nitrogen-containing extractives, cho- 

 Jesterin, lactosen (a carbohydrate), orotic acid, a pigment, citric 

 acid, a mucin (lactomucin), gases, and besides these chemical 

 compounds, enzyms, and antibodies. The milk enzyms are either 

 products of the milk glands or of bacteria which are always pres- 

 ent in the udder. The antibodies are transmitted from the 

 maternal system to the young through milk. 



Some chemical compounds have frequently been isolated from 

 milk, such as amino-acids, ammonia, hydrogen sulphid, marsh- 

 gas, and others, but it is doubtful whether these are normal con- 

 stituents of milk, or whether they are formed by microbial action 



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